The present invention relates to paging networks. In particular, one embodiment of the present invention provides an improved paging network which uses satellites to fill gaps in FM station coverage.
Paging networks generally operate by broadcasting small packets of data which are addressed to specific pagers. A pager listens to the broadcasts and responds to those packets addressed to that pager.
One way to broadcast messages is to use subcarriers of existing radio stations. This avoids the need for the operator of a paging network to purchase and maintain separate broadcast equipment. A standard FM radio station broadcasts up to five subchannels on subcarriers of 0 Khz, 19 Khz, 38 Khz, 57 Khz and 68 Khz. The first two subcarriers are used for mono and stereo transmission, respectively, of the radio station broadcast picked up by ordinary radio receivers. The other three subcarriers are known as SCA (Secondary Channel Authority) subcarriers, and can be used to carry audio or data transmissions for receipt by specially configured receivers. Where a paging network broadcasts using the SCA subcarriers of the radio station, the pagers are configured to listen to a particular subcarrier band and decode data thereon, looking for messages with that pager's address. Many thousands of such pagers are in use today and therefore can be made inexpensively. Another simplification in the pager market has been the standardization of protocols, so that most pagers made today for SCA use have been standardized.
Because it is difficult to cover a large geographic region, such as the North America continent, with continuous radio coverage, a paging network might have gaps in coverage. If a pager is in an uncovered area, it will not receive messages sent to it. Since pagers are generally receive-only, the paging network does not have a way to ensure that the pager received a message, therefore it is incumbent on the paging network to make efforts to ensure coverage.
Of course, pagers would be more likely to receive signals if they have better antennae, higher power, etc. Unfortunately, longer range pagers are often unsuitable for applications where the user of the pager wants a compact, light device to carry around.
Therefore, what is needed is a system for increasing pager reception without adding to the bulk of a pager. Preferably, the increase must be done without modifying the design of the basic, standardized pager.